Cells Of Rat Parotid Gland Research Articles

A guanine nucleotide-dependent regulatory protein couples substance P receptors to phospholipase C in rat parotid gland

Electrically permeabilized cells of rat parotid gland, prelabelled with [ 3H]-inositol, synthesized [ 3H]-inositol phosphates (IP 3 and IP 2) when stimulated with α 1-adrenergic, muscarinic-cholinergic, and substance P receptoragonists. Non-hydrolyzable analogues of GTP (GTPγS and GppNHp) also stimulated [ 3H]-IP 3 formation by permeabilized cells and they potentiated the stimulation by receptor-agonists. These effects of guanine nucleotides occurred only with GTP analogues and only in permeabilized cells indicating an intracellular site of action. NaF stimulated [ 3H]-IP 3 accumulation, an effect that was not entirely attributable to the ability of F- to inhibit (1,4,5)IP 3 degradation. These results suggest that a guanine nucleotide-dependent regulatory protein couples Ca 2+-mobilizing receptors to phospholipase C in parotid gland.

Anti-substance P anti-idiotypic antibodies. Characterization and biological activities.

Antibodies to substance P (SP) produced in rabbits have been characterized for their specificity toward SP and some 30 SP-related peptides. For each compound, we observed a close correlation between capacity of binding to anti-SP antibodies and biological activity, namely their spasmogenic effect on guinea pig ileum in vitro and their hypotensive effect in the rat in vivo, indicating that the combining sites of anti-SP and SP receptor(s) are structurally very similar. Further immunization of five rabbits with anti-SP immunoglobulins elicited in two allotype-matched animals the production of anti-SP anti-idiotypic antibodies. These latter antibodies were found to strongly inhibit the spasmogenic action of SP on the guinea pig ileum. In contrast, they specifically enhanced, like SP, phospholipid turnover in rat parotid gland cells, a physiological function mediated through an activation of SP receptors. Immunocytochemical studies actually revealed the presence of specific membranous binding sites for anti-idiotypic antibodies on the parotid gland-dissociated cells. The anti-idiotypic antibodies described here, which thus behave either as agonists or antagonists for SP depending on the biological test, might be used as original and powerful tools not only in studies of the receptor stereospecificity but also in attempts to purify the membranous SP receptors.

Tracer uptake by duct cells of rat parotid gland

Tracer uptake by duct cells of rat parotid gland

Beta-Adrenergic receptor regulation of N-linked protein glycosylation in rat parotid acinar cells.

We have investigated the relationship between beta-adrenergic receptor stimulation and protein glycosylation and secretion in rat parotid gland cells in vitro. The potent beta-adrenergic agonist (-)-isoproterenol increases [3H]mannose incorporation into newly synthesized glycoproteins. This effect is enhanced if cells are first preincubated with dolichyl phosphate and is not observed after muscarinic-cholinergic or alpha-adrenergic stimulation of cells. The increase in [3H]mannose incorporation is abolished by incubation of cells with tunicamycin, suggesting that the glycosylation events being studied involved asparagine-linked oligosaccharides. The extent of increase in glycosylation is dependent on the concentration of (-)-isoproterenol to which cells are exposed. (+/-)-Propanolol totally abolishes the (-)-isoproterenol-induced increase in [3H]mannose incorporation, in a manner similar to its effects on exocrine secretion. Our findings suggest that beta-adrenergic receptor activation has a profound influence on N-linked protein glycosylation in rat parotid cells in addition to eliciting exocrine protein release.

Inhibitory effect of carbachol on isoproterenol-induced amy lase release from isolated rat parotid acinar cells

We previously reported that carbachol(CCh) inhibits isoproterenol(ISP)-induced amylase release from isolated rat parotid acinar cells. The present study was undertaken to clarify the mechanism of inhibitory effect of CCh on ISP-induced amylase release. Dispersed acinar cells of rat parotid glands were incubated at 37°C in modified Krebs-Ringer-Tris medium(KRT) for 30min. The following results were obtained: 1) I SP(10-6M)-induced amylase release was inhibited by the pretreatment of CCh(10−6 - 10−4M). 2)The inhibitory effect was blocked by a tropi ne (10”), and also the effect disappeared in Ca-free(1mM EGTA) KRT. 3) ISP(10−6M) - induced increase in cyclic AMP was not affected by CCh(10−5M) in either normal or Ca-free KRT. 4)Ca ionophore A231 87(10-5M) markedly inhibited the ISP-induced amy lase release. 5)Both CCh(10-5M) and ISP(10-6M) increased 45Ca uptake and its efflux. CCh significantly enhanced the effect of ISP on 45ca uptake. These results suggest that Ca2+ influx may play an important role in the inhibitory effect of CCh on ISP-induced amylase release from isolated rat parotid acinar cells.

K + release from rat parotid cells: An α 1-adrenergic mediated event

To characterize α-adrenergic receptors in rat parotid gland tissue, 9,10-[9,10- 3H(N)]-dihydro-α-ergocryptine ([ 3h]dhe) and [ 3H]prazosin binding to membranes and stimulated K + release from parotid cell aggregates were examined. Prazosin (selective α 1-adrenergic antagonist), displacement of [ 3H]DHE binding from parotid membranes was biphasic, indicating the presence of both α 1- and α 2-adrenergic receptors. The numbers of α 1- and α 2-receptors were about equal. α 1-Adrenergic receptors were further studied by [ 3H]prazosin binding. [ 3H]Prazosin binding was a rapid, reversible, saturable and stereospecific process, with high affinity ( K D = 0.38 nM) and low capacity ( B max = 380 fmoles ligand bound/g tissue, 10.1 fmoles/mg protein) as determined by Scatchard analysis. The characteristics of [ 3H]prazosin binding were in good agreement with those of catecholamine-stimulated K + release, suggesting that K + release from rat parotid gland cells is an α 1-adrenergic mediated effect.

Rate of protein synthesis in rat salivary gland cells after pilocarpine or feeding. III. Protein synthesis in vitro in the submandibular and parotid gland after stimulation of secretion in vivo.

After stimulation of the protein secretion by pilocarpine or feeding the rate of incorporation of [3H]-leucine increases in the acinar cells of the parotid gland of the rat while the secretory cells of the submandibular gland show a moderate decrease (Kuijper et al., 1975b). Since the rate of labelled amino acid incorporation depends on the specific radioactivity of the amino acid used, which is not easy to determine in vivo, experiments in vitro were performed to get an idea of the influence of this factor on the measured changes in [3H]-leucine incorporation. In vitro both cell types showed a more pronounced but essentially identical reaction as in vivo. Since in these experiments the specific radioactivity of the extracellular leucine is the same whether fragments of stimulated or unstimulated glands incorporate the radioactive amino acid, the increase of incorporation in the parotid and the decrease in the submandibular cells cannot be ascribed to differences in specific radioactivity of leucine, unless the intracellular leucine pool should show great differences between secreting and non-secreting cells. However, in vitro the submandibular gland cells under both conditions appear to use the extracellular leucine for their protein synthesis (or a small compartmentalized pool in rapid exchange with the extracellular pool). In the parotid cells the whole intracellular pool showed such a rapid exchange with the extracellular one that for practical reasons one may say that these cells, too, rely on the extracellular specific radioactivity of leucine in their protein synthesis. We conclude that the rat parotid gland cells show a rapid and substantial increase of protein synthesis after stimulation of their enzyme secretion, while the submandibular gland cells do not.